title: Disease-causing mutations in the XIAP BIR2 domain impair NOD2-dependent immune signalling.
abstract: X-linked Inhibitor of Apoptosis (XIAP) is an essential ubiquitin ligase for pro-inflammatory signalling downstream of the nucleotide-binding oligomerization domain containing (NOD)-1 and -2 pattern recognition receptors. Mutations in XIAP cause X-linked lymphoproliferative syndrome type-2 (XLP2), an immunodeficiency associated with a potentially fatal deregulation of the immune system, whose aetiology is not well understood. Here, we identify the XIAP baculovirus IAP repeat (BIR)2 domain as a hotspot for missense mutations in XLP2. We demonstrate that XLP2-BIR2 mutations severely impair NOD1/2-dependent immune signalling in primary cells from XLP2 patients and in reconstituted XIAP-deficient cell lines. XLP2-BIR2 mutations abolish the XIAP-RIPK2 interaction resulting in impaired ubiquitylation of RIPK2 and recruitment of linear ubiquitin chain assembly complex (LUBAC) to the NOD2-complex. We show that the RIPK2 binding site in XIAP overlaps with the BIR2 IBM-binding pocket and find that a bivalent Smac mimetic compound (SMC) potently antagonises XIAP function downstream of NOD2 to limit signalling. These findings suggest that impaired immune signalling in response to NOD1/2 stimulation is a general defect in XLP2 and demonstrate that the XIAP BIR2-RIPK2 interaction may be targeted pharmacologically to modulate inflammatory signalling.
authors.affiliation: Department of Disease Biology, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Rune Busk
authors.initials: RB
authors.lastname: Damgaard
authors.forename: Berthe Katrine
authors.initials: BK
authors.lastname: Fiil
authors.forename: Carsten
authors.initials: C
authors.lastname: Speckmann
authors.forename: Monica
authors.initials: M
authors.lastname: Yabal
authors.forename: Udo
authors.initials: U
authors.lastname: zur Stadt
authors.forename: Simon
authors.initials: S
authors.lastname: Bekker-Jensen
authors.forename: Philipp J
authors.initials: PJ
authors.lastname: Jost
authors.forename: Stephan
authors.initials: S
authors.lastname: Ehl
authors.forename: Niels
authors.initials: N
authors.lastname: Mailand
authors.forename: Mads
authors.initials: M
authors.lastname: Gyrd-Hansen
mesh_terms: D017209:Apoptosis; D001665:Binding Sites; D045744:Cell Line, Tumor; D057809:HEK293 Cells; D006801:Humans; D007249:Inflammation / Q000276:immunology*; D020125:Mutation, Missense; D053473:Nod2 Signaling Adaptor Protein / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D015398:Signal Transduction; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics* / Q000502:physiology
chemical_list: C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D025801:Ubiquitin; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2
keywords: BIR2; NOD2; Smac mimetic compounds; XIAP; XLP2